{{Merge|Network Configuration|already duplicates part of its content}}

This article handles the steps needed for basic network troubleshooting.

This article handles the steps needed for basic network troubleshooting.

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==iproute2==

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Many users are familiar with tools like {{ic|ifconfig}} and {{ic|route}}, but the related package ({{pkg|net-tools}}) has been [https://www.archlinux.org/news/deprecation-of-net-tools/ deprecated] for a while. All its functionalities can now be found in the replacement {{pkg|iproute2}} package, included in a standard Arch Linux core installation and required by tools like [[netcfg]] and [[networkmanager]].

==Network Interfaces==

==Network Interfaces==

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The first step in troubleshooting network issues will be to identify which network interfaces are present on the system. This can be done by issuing the command:

+

The first step in troubleshooting network issues will be to identify which network interfaces are present on the system. See [[Network configuration#Get current device names]] for details.

DNS Servers

Dns is responsible for converting hostnames to an ip address. When connectivity towards ip addresses is working, but the system is unable to connect to a hostname; there is a fair chance that this will be related to the dns configuration. The configuration can be displayed by running:

$ cat /etc/resolv.conf

This will provide an output among the lines of:

domain example.com
search example.com
nameserver 192.168.1.1

The rule 'nameserver' is the relevant section. Configuring multiple nameservers is supported.

The 'domain' and 'search' rules are optional.

Often the 'nameserver' is the same as your default gateway.

In case of doubt there is always the possibility to use the Google DNS servers as your default DNS servers:

nameserver 8.8.8.8
nameserver 8.8.4.4

Testing your dns configuration can be done through the drill command (from the ldns package):

$ drill www.archlinux.org @8.8.4.4

The above command will perform a dns lookup of www.archlinux.org using the 8.8.4.4 dns server and return output as follows:

The output above indicated the default gateway is reachable. When instead a "Destination Host Unreachable" message is displayed, doublecheck the ip address, netmask and default gateway config. This message can also be displayed when ICMP traffic is not permitted towards the default gateway (blocked by a firewall, router,...).

The next step is verifying connectivity towards the configured dns server(s). When no reply is received, tracepath or traceroute can be used to verify the routing towards said server and get an idea of where the issue lies.

$ traceroute 8.8.4.4

Traceroute also used ICMP to determine the path and hence there can be "no reply" answers as well when ICMP traffic is blocked.